Devices are known from the prior art that have matrices of active pixels, in which each pixel comprises an OLED diode and a control circuit constructed from transistors. In these matrices, the cathodes of the OLED diodes are coupled together to receive a cathode voltage, for example a negative voltage.
The OLED diodes exhibit a voltage threshold which can vary with temperature. To obtain a light image which is unaffected by temperature, it has been proposed to use a temperature sensor, and to use the measured temperature value to generate a cathode voltage which makes it possible to maintain the light emission despite the temperature variation.
This approach presents a variety of drawbacks. For example, a calibration step after the fabrication of each device is used to associate the temperature values with the corresponding cathode voltage levels and with the luminosity levels. This step can be time consuming, and the temperature sensors used may not be sufficiently accurate with an inaccuracy on the order of a few degrees. The circuitry used to generate a cathode voltage may not be sufficiently accurate, and the use of a single temperature sensor provides information relating to the temperature at but a single point.
Therefore, further developments in devices with matrices of active OLED pixels capable of compensating for temperature are desired.